Electromagnetic switch.



R. H. McLAlN.

ELECTROMAGNETIC SWITCH. APPLICATION FILED |MY|2.1911.

1,177,427. I I v Patgnted Mar. 28,1916.

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UNITED STATES PATENT ormca.

ROBERT E. IOLAIN, OI SCHE1.TlilC'llAIlIiY, YORK, ASSIGNOB TO GENERAL ELECTRIC COMPANY, A CORPORATION OF NEW. YORK.

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Specification of Letters latent.

Application flied Kay 12, 1911. Serial No. 628,800.

To all whom it may concern:

Be it known that I, ROBERT H. MCLAIN,

' a citizen of the United States, residin at .opened or closed and the condition under which the opening or closure takes place suitably adjusted in a simple and reliable manner. 1

My invention relates more specifically to electromagnetic switches for controlling the circuit of translating devices, such as electric motors and the like. Switches of this character are commonly provided with an actuating'winding and a core" actuated thereby and cooperating with the switch member. Such a switch'is moved in one direction by the magnet winding to either open or close a circuit and is then moved in the opposite direction either by gravity or a spring. The number of ampere turns necessary for lifting the core is considerably greater than'that at which the switch will be released. Ordinarily, however, the pickup current and the releasing-current bear a definite relation to each other. It is frequently desirable, therefore, to be able to adjust the current at which the switch. will drop out or release independently of the pickup current. I can be .done in a satisfactory manner in alternating current circuits by arranging an auxiliary winding in inductive relation to said first winding so as to be acted upon thereby 'with a transformer action, 1n such a way as to oppose or buck the effect of the first winding. By providing a resistance in,

the ,circuit of said auxiliary winding the opposing effect may be varied.

In theaccompanying drawing in which I have illustrated my-inventionas ooerating in a manner to accomplish aspecific result Figure 1 is a diagram 'of the circuit connections: netic switch or relay. I

In the arrangement shown'in Fig. 1, A

and B represent two induction motors connected to a common driving shaft which in .turn is connected to drive other machines have found that this and Fig. 2-shows the electromag through belt 10. These motors are intended to be connected to operate together only when the load justifies it; that is, when the load upon the motor A becomes heavy enough, the motor B will be automatically connected in circuit. This is accomplished by the useof my improved form of electromagnetic switch or relay. In a' system of this character it is desirable, of course, that the load at which the second motor will be thrown in be adjustable. It is also desirable that the olnt at which the second motor is Patented Mar. 28, 1916.

cut out s all be adjustable independently of the adjustment for throwing the motor in. For accomplishing this resultI have provlded a re ay C which consists of a main actuating winding. 11 connected in series with one phase of the motor A and having a core for operating the switch contact 12. An auxiliary winding 13 is mounted upon the same core as the winding 11 and is inductively related thereto so as, to be acted upon by transformer action. In the circuitv of this winding 13 is'an adjustable rheostat R. The circuit of the winding 13 is normally open at the contact 14. This contact 14 is closed by means of a winding 15 energized through the contact 12. The winding 15 likewise closes the contacts 16'which conn ect the motor B in circuit.

The electromagnetic switch or relay C, which is one of the features of my invention, consists of a magnetic frame 17 and a core operatingtherein. This core isdivided into two parts 18 and 19 held together by a nonmagnetic screw 20 so as to form an air gap between the two cores. This air gap may 'be adjusted by screwing the lower. core 19 toward and away from the upper core. The two windings 11 and 13 are mounted upon the compound core. When the winding 11 is connected with an alternating current circuit, a current will be induced'in the wind- 13 is closed. Assuming that the circuit of winding 11 is first closed on alternating current, the magnetic flux is from the core through the air gap 21 between the upper part of the core and .the iron frame, aroun through the iron, frame'to the bottom core 19 and through the air gap 22. The-core will then be pulled uoand the switch contact '12 will be closed.

The currentinthe winding 11 at which the core will rise may be 'varied by varying the width of the air gap 22. Ordinarily the a fixed relation to the current at which the core will release. In order to vary this relation and increase the current value in the winding 11 at which. the core will be released I have provided the winding When the circuit'of the winding 13 is closed, the flux due to the transformer action between thetwo coils 11 and 13 opposes the flux due to the winding 11 alone. This has the effect of off-setting to a certain extent the effect of the winding 11, and causing the core to be dropped at a higher current in the winding 11. That is, assuming that it takes ten amperes in the coil 11.to lift the core it will then take considerably less to hold up the core, say, for instance, three amperes. The core-will therefore drop when the current in the winding falls .below three amperes. When, however, the winding 13 is energized, the holding effect of the current in coil 11 is decreased so that it will take more current to hold up the core. The core will therefore drop at a higher current in the winding 11. By varying the resistance in the circuit of the winding 13 at the rheostat R the effect of the winding 13 may be varied. This operation, however, does not aflect the current at which the coil 11 will pick up the core. Furthermore, the adjustment of the lower core for the purpose of calibrating the point at which the core will vpick up does not materially affect the lower winding and what little effect it does have may be offset by the resistance of the rheostat R.

Referring now to the operation of the system shown in Fig. 1, it will be seen that the motor A is connected with the three phase mains a, b, c, the coil 11 being connected to phase a. WVhen the motor current rises to a predetermined point, the actuating winding 11 of relay C will lift the contact 12, thereby energizing the winding 15 and throwing the motor B upon the line. At the same time that the motor B is connected in circuit, the auxiliary winding 13 of the relay C is closed at the contact 14. For the reasons above explained, the cutting in of the winding 13 increases the current at which the relay C Will drop out and thereby the load at which the motor B will be disconnected. The rheostat R is employed forv varying the point at which the motor B is cut out..

It will be seen'that I have provided a simple and efiective means whereby-the operation of an electromagnetic switch is varied and While I have described my invention as applied to a particular system and asoperating in a specific manner, it should be understood that I do not limit my invention thereto, sincevarious modifications thereof will suggest themselves 'to those skilled in the art without departing from the spirit of my invention, the scope of which is set.

forth in the annexed claims.

What I claim as new and desire-to secure by Letters Patent of the United States, is,

the same to closed position, a second winding acting .upon sald switch member and eneri gized by induction from said first winding upon the closing of said switchin opposition to said. first winding so as to increase the current value at which the switch mem-' ber will open, and means for adjusting the value of current at which the switch memher is lifted without affecting the value at which the switch will open. I

2. An electromagnetic switch for alternatingcurrent circuits comprising. a switch member, an actuating windingfor lifting the same to'closed position, a second winding acting upon said switch member and energized by lnduction from said first winding upon the closing of said switch in opposition to said first winding so as to increase the current value at which the. switch member will open, and means for varying the impedance of the circuit of said second winding.

3. An electromagnetic switch for alternating currentvcircuits comprising an actuating winding and a core therefor, a normally open-circu'ited second winding having a core movable with said first core and energized by induction from said first Winding, a' contact member operated by the movement of said cores, means for closing the circuit ofsaid secondwinding upon the lifting of said contact member by the actuating winding, and means for adjusting said cores with reference to each other.

4. An electromagnetic switch for alternating current circuits comprising an actuating winding and a core therefor, a normally open circuited second winding having a core movable with said first core and energized by induction from said first winding so as to generate a flux in opposition to the flux of the first winding, a contact member operated by the movement of said cores,

means for closing the circuit of said second,

winding. upon the'closing of said contact member by the actuating winding, means for adiusting said cores with-reference to 

